643720565407 has 2 divisors, whose sum is σ = 643720565408. Its totient is φ = 643720565406.

The previous prime is 643720565357. The next prime is 643720565413. The reversal of 643720565407 is 704565027346.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643720565407 - 2¹¹ = 643720563359 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643720565447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321860282703 + 321860282704.

It is an arithmetic number, because the mean of its divisors is an integer number (321860282704).

Almost surely, 2^643720565407 is an apocalyptic number.

643720565407 is a deficient number, since it is larger than the sum of its proper divisors (1).

643720565407 is an equidigital number, since it uses as much as digits as its factorization.

643720565407 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4233600, while the sum is 49.

The spelling of 643720565407 in words is "six hundred forty-three billion, seven hundred twenty million, five hundred sixty-five thousand, four hundred seven".